Process of preparing in-situ water-soluble zinc salt for use in automatic dishwashing compositions

ABSTRACT

A process for preparing in-situ water-soluble zinc salts for use in automatic dishwashing compositions is disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S. PatentApplication No. 60/437,077 filed Dec. 30, 2002, the disclosure of whichis incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to water-soluble zinc salts and theirpreparation for use in automatic dishwashing compositions and/orproducts. More specifically, it relates to preparing in-situwater-soluble zinc salts for use in rinse aid and detergentcompositions.

BACKGROUND OF THE INVENTION

Automatic dishwashing compositions which provide glassware protectionare well known. The use of water-soluble zinc salts, such as zinc saltsof chloride, sulfate or acetate, have been disclosed for this purpose. Awater-soluble zinc salt can be employed to prevent the corrosion ofceramic surfaces. Solid plates of slowly dissolving zinc metal alloyscan be placed in contact with a detergent composition or low-foamingnonionic surfactant to provide corrosion protection to glassware. Infact, insoluble inorganic zinc compounds can also be employed inconjunction with a surfactant for similar purposes. Though zincgluconate has been prepared in-situ for use in a liquid dishwashingdetergent composition, there remains a need to provide a cost-effectiveprocess of preparing in-situ water-soluble zinc salts for use insuitable automatic dishwashing compositions and/or products to helpprevent glassware corrosion.

It has surprisingly been found that cost effective water-soluble zincsalts may be prepared in-situ for use in automatic dishwashingcompositions and/or products. These water-soluble zinc salts whenprepared in-situ and combined to form a rinse aid composition providesprotection from glassware corrosion during the rinse cycle and promoteconsumer satisfaction in automatic dishwashing results.

SUMMARY OF THE INVENTION

The present invention relates to a process for preparing a water-solublezinc salt in-situ for use as a base or additive in preparing anautomatic dishwashing rinse aid composition. The process comprises thesteps of: (a) dispersing zinc oxide in water; (b) combining an acid withthe zinc oxide/water mixture; (c) mixing the zinc oxide/water mixtureand the acid until the zinc oxide is at least partially dissolved; (d)maintaining the zinc oxide/water/acid mixture within an acidic pH range;and (e) combining the zinc oxide/water/acid mixture with at least onerinse aid ingredient to form the rinse aid composition.

The present invention also relates to a process for preparing awater-soluble zinc salt in-situ for use as a base or additive inpreparing an automatic dishwashing detergent composition. The processcomprises the steps of: (a) dispersing zinc oxide in water; (b)combining an acid with the zinc oxide/water mixture; wherein the acid isselected from the group consisting of acetic acid, aspartic acid,benzoic acid, boric acid, bromic acid, formic acid, glutamic acid,hydrochloric acid, lactic acid, malic acid, nitric acid, sulfamic acid,sulfuric acid, tartaric acid, and mixtures thereof; (c) mixing the zincoxide/water mixture and the acid until the zinc oxide is at leastpartially dissolved; and (d) combining the zinc oxide/water/acid mixturewith at least one deterrent ingredient to form the detergentcomposition.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to water-soluble zinc salts and theirpreparation for use in automatic dishwashing compositions and/orproducts. Automatic dishwashing compositions include, but are notlimited to, detergent compositions, rinse aid compositions, andcombinations thereof. The preparation of in-situ zinc salt disclosedherein requires zinc oxide to be dispersed in water and combined with anacid. The resulting mixture may be designed to be the base or added asan additive in a process for making or preparing an automaticdishwashing composition and/or product, such as a detergent and/or rinseaid composition.

Water-soluble zinc salts may be prepared in-situ by reacting zinc oxidewith an acid according to the general formula:2H_(x)A+XZnO→XZnA_(2/x)+XH₂Owherein A is an organic and/or an inorganic acid, and x is an integerthat varies from 1 to 2. For example, water-soluble zinc nitrate can beprepared in-situ by reacting zinc oxide with nitric acid according tothe formula:2HNO₃+ZnO→Zn(NO₃)₂+H₂OThe zinc oxide may be provided in any suitable amount. A suitable amountof zinc oxide is an amount that will deliver via an automaticdishwashing composition and/or product from about 0.01 mM to about 10mM, alternatively about 0.02 mM to about 5 mM, alternatively about 0.05mM to about 1 mM, and alternatively about 0.05 mM to about 0.5 mM of awater-soluble zinc salt compound or product to the wash and/or rinseliquor of an automatic dishwashing appliance during operation.Alternatively, a suitable amount of zinc oxide is an amount that willdeliver via an automatic dishwashing composition and/or product fromabout 0.1 ppm to about 60 ppm, alternatively from about 0.1 ppm to about30 ppm, alternatively from about 0.1 ppm to about 15 ppm, and/oralternatively from about 0.1 ppm to about 10 ppm of a water-soluble zincsalt compound or product to the wash and/or rinse liquor of an automaticdishwashing appliance during operation.

The zinc oxide may be provided in any suitable form. For example, thezinc oxide may be in powder form. The zinc oxide is first dispersed inwater. At least a stoichiometric amount according to the above generalformula, or alternatively a slight excess, of an acid is added slowly tothe dispersion.

The mixture is then stirred continuously until the zinc oxide is atleast partially dissolved, and alternatively fully dissolved. The orderof addition of the process steps of the in-situ preparation of the zincoxide/water/acid mixture is not critical. Thus, the process can firststart with the addition of the acid, followed by zinc oxide dispersed inwater—the later of which is slowly added with continuous stirring untilthe zinc oxide is fully dissolved or vice versa. Once the zinc oxide isat least partially dissolved, the zinc oxide/water/acid mixture willbegin to clear. Once the zinc oxide/water/acid mixture is fullydissolved it will exhibit a clear solution. This completes the in-situacid neutralization process.

After the in-situ acid neutralization process is completed, any suitableamount of a suitable automatic dishwashing ingredient can be admixed inany order with the zinc oxide/water/acid mixture to make the desiredautomatic dishwashing composition. Suitable automatic dishwashingingredients that may be added to the zinc oxide/water/acid mixture toprepare a rinse aid composition and/or product include, but are notlimited to: an acid, a hydrotrope, a thickener, a binder, a dispersantpolymer, a carrier medium, a surfactant, a perfume, a dye, and mixturesthereof. Suitable automatic dishwashing ingredients that may be added tothe zinc oxide/water/acid mixture to prepare a detergent compositionand/or product include, but are not limited to: a detergent builder,alkalinity builder, bleach, enzyme, surfactant, defoamer, polymer,bleach activator, and mixtures thereof.

For example, citric acid, sodium cumene sulfonate, Acusol® polymer,ethanol, non-ionic surfactant, perfume, dye, and mixtures thereof may beadded sequentially to the zinc oxide/water/acid mixture to make a liquidrinse aid composition and/or product. In another example, a binder or asolid surfactant (e.g. solid at 25° C.) may be added to formulate asolid rinse aid composition. In another example, a detergent builder, anenzyme, surfactant, a defoamer, and mixtures thereof may be added to thezinc oxide/water/acid mixture to formulate a liquid detergentcomposition. In yet another example, an alkalinity builder, asurfactant, a bleach, a bleach activator, and mixtures thereof may beadded to the zinc oxide/water/acid mixture to formulate a soliddetergent composition.

Acid

Any suitable organic and/or inorganic acid in any suitable amount may beused to prepare in-situ water-soluble zinc salts for use in automaticdishwashing rinse aid compositions and/or products. Some suitable acidsto be used the in-situ water-soluble zinc salt preparation processinclude, but are not limited to: acetic acid, aspartic acid, benzoicacid, boric acid, bromic acid, formic acid, gluconic acid, glutamicacid, hydrochloric acid, lactic acid, malic acid, nitric acid, sulfamicacid, sulfuric acid, tartaric acid, and mixtures thereof.

Any acid that leads to precipitation of the zinc salt should not be usedin the in-situ water-soluble zinc salt preparation process. For example,citric acid leads to precipitation of an insoluble zinc salt. However,as disclosed below, such precipitation acids may be added to the mixtureafter the in-situ process is completed.

Adding an acid after the in-situ water-soluble zinc salt preparationprocess, such as in the preparation of an automatic dishwashingcomposition, enables the water-soluble zinc salt to at least partiallydissolve, alternatively to fully dissolve, and alternatively remaindissolved. The acid may act to stabilize the composition againstprecipitation in the product prior to use. The acid also helps toeliminate precipitation on hard surfaces, such as on flatware, glasses,dishes and/or components inside the automatic dishwashing applianceitself, during the wash and/or rinse cycle.

When preparing in-situ water-soluble zinc salts to be used in solidrinse aid composition, certain non-precipitation acids will not resultin precipitation of the water-soluble zinc salt in the rinse aidcomposition and/or product itself or in rinse liquor of the automaticdishwashing appliance during operation. For example, nitric acid,hydrochloric acid, and mixtures thereof, are typically non-precipitationacids. Conversely, precipitation acids, like phosphoric acid, citricacid, and mixtures thereof, may result in precipitation of an insolublezinc salt during preparation of in-situ water-soluble zinc salts. Forexample, a precipitation acid may be added only after the water-solublezinc salt is at least first partially dissolved, and alternatively fullydissolved, in a non-precipitation acid, such as nitric acid,hydrochloric acid, and mixtures thereof. Furthermore, the dissolvedwater-soluble zinc salt (i.e. those dissolved in a non-precipitationacid) should have the pH maintained in the acidic pH range prior toadding a subsequent precipitating acid to the mixture in order toprevent insoluble materials from forming in the rinse aid compositionand/or product itself, or in the rinse liquor of the automaticdishwashing appliance during the rinse cycle. A suitable amount of acidmay be determined stoichimetrically using the formula:2H_(x)A+XZnO→XZnA_(2/x)+XH₂Owherein A is an organic and/or an inorganic acid, and x is an integerthat varies from 1 to 2. Suitable acids are typically present in thepreparation of in-situ water-soluble zinc salt range from about 0.01% toabout 25%, alternatively from about 0.5% to about 20%, and alternativelyfrom about 1% to about 10%, by weight of the mixture.

In one non-limiting embodiment, an acid selected from the groupconsisting of acetic acid, formic acid, gluconic acid, glutamic acid,hydrochloric acid, malic acid, nitric acid, sulfuric acid, and mixturesthereof, by weight of the mixture may be used in the preparation ofin-situ water-soluble zinc salt.

pH

The pH of the zinc oxide/water/acid mixture may be measured directly atthe end of the in-situ process. However, when the zinc oxide/water/acidmixture is combined with at least one rinse aid ingredient to form arinse aid composition, the pH of the rinse aid composition should bemeasured as a 10% concentration in an aqueous solution.

Suitable pHs range from about 1 to about 5, alternatively from about 1to about 4, and alternatively from about 1 to about 3. A lower acidic pHrange will tend to reduce incompatibility and negative interaction ofrinse aid ingredients. A slightly higher acidic pH range will allow forsome flexibility in product formulation.

Zinc Salts Prepared Using In-Situ Process

Any suitable water-soluble salt of zinc in any suitable amount may beprepared in-situ by reacting zinc oxide with an inorganic and/or organicacid. In-situ water-soluble zinc salts suitable for use in automaticdishwashing can be prepared for use in liquid compositions and/orproducts, solid compositions and/or products, and mixtures thereof.

Water-soluble zinc salts that may be prepared in-situ include, but arenot limited to: zinc acetate, zinc benzoate, zinc borate, zinc bromide,zinc chloride, zinc formate, zinc gluconate, zinc lactate, zinc laurate,zinc malate, zinc nitrate, zinc perborate, zinc sulfate, zinc sulfamate,zinc tartrate, and mixtures thereof.

The in-situ water-soluble zinc salt prepared by this process may existin any physical form, including, but not limited to, liquid, solid, andcombinations thereof. The in-situ water-soluble zinc salt may becombined with automatic dishwashing ingredients to form an automaticdishwashing composition which may also exist in any physical form,including, but not limited to, liquid, solid, and combinations thereof.

The disclosure of all patents, patent applications (and any patentswhich issue thereon, as well as any corresponding published foreignpatent applications), and publications mentioned throughout thisdescription are hereby incorporated by reference herein. It is expresslynot admitted, however, that any of the documents incorporated byreference herein teach or disclose the present invention.

It should be understood that every maximum numerical limitation giventhroughout this specification would include every lower numericallimitation, as if such lower numerical limitations were expresslywritten herein. Every minimum numerical limitation given throughout thisspecification will include every higher numerical limitation, as if suchhigher numerical limitations were expressly written herein. Everynumerical range given throughout this specification will include everynarrower numerical range that falls within such broader numerical range,as if such narrower numerical ranges were all expressly written herein.

While particular embodiments of the subject invention have beendescribed, it will be obvious to those skilled in the art that variouschanges and modifications of the subject invention can be made withoutdeparting from the spirit and scope of the invention. It will be clearto those skilled in the art that various changes and modifications maybe made without departing from the scope of the invention and theinvention is not to be considered limited to the embodiments andexamples that are described in the specification.

1. A process for preparing an in-situ water-soluble zinc salt for use asa base or additive in preparing an automatic dishwashing composition,said process comprising the steps of: a) dispersing zinc oxide in water;b) combining an acid with said zinc oxide/water mixture; c) mixing saidzinc oxide/water mixture and said acid until said zinc oxide is at leastpartially dissolved; d) maintaining said zinc oxide/water/acid mixturewithin an acidic pH range; and e) combining said zinc oxide/water/acidmixture with at least one rinse aid ingredient to form a rinse aidcomposition; wherein the order of addition of said process steps (a) and(b) is not critical.
 2. A process according to claim 1, wherein saidzinc oxide/water/acid mixture has a pH of less than about
 5. 3. Aprocess according to claim 1, wherein zinc oxide is provided in anamount that will deliver via an automatic dishwashing composition and/orproduct from about 0.01 mM to about 10 mM of a water-soluble zinc saltcompound or product to the wash and/or rinse liquor of an automaticdishwashing appliance during operation.
 4. A process according to claim3, wherein from about 0.02 mM to about 5 mM of said water-soluble zincsalt compound or product is delivered.
 5. A process according to claim4, wherein from about 0.05 mM to about 1 mM of said water-soluble zincsalt compound or product is delivered.
 6. A process according to claim5, wherein from about 0.05 mM to about 0.5 mM of said water-soluble zincsalt compound or product is delivered.
 7. A process according to claim1, wherein said acid is provided at least in an amount determinedstoichimetrically using the formula:2H_(x)A+XZnO→XZnA_(2/x)+XH₂O wherein A is an organic and/or an inorganicacid, and x is an integer that varies from 1 to
 2. 8. A processaccording to claim 1, wherein said acid is selected from the groupconsisting of acetic acid, aspartic acid, benzoic acid, boric acid,bromic acid, formic acid, gluconic acid, glutamic acid, hydrochloricacid, lactic acid, malic acid, nitric acid, sulfamic acid, sulfuricacid, tartaric acid, and mixtures thereof.
 9. A process according toclaim 1, wherein said acid is acetic acid.
 10. A process according toclaim 1, wherein said acid is gluconic acid.
 11. A process according toclaim 1, wherein said acid is hydrochloric acid.
 12. A process accordingto claim 1, wherein said acid is nitric acid.
 13. A process according toclaim 1, wherein a water-soluble zinc salt is prepared in-situ, whereinsaid salt is selected from the group consisting of zinc acetate, zincbenzoate, zinc borate, zinc bromide, zinc chloride, zinc formate, zincgluconate, zinc lactate, zinc laurate, zinc malate, zinc nitrate, zincperborate, zinc sulfate, zinc sulfamate, zinc tartrate, and mixturesthereof.
 14. A process according to claim 1, wherein said in-situprepared water-soluble salt is zinc acetate.
 15. A process according toclaim 1, wherein said in-situ prepared water-soluble salt is zincgluconate.
 16. A process according to claim 1, wherein said in-situprepared water-soluble salt is zinc chloride.
 17. A process according toclaim 1, wherein said in-situ prepared water-soluble salt is zincnitrate.
 18. A process according to claim 1, wherein said at least onerinse aid ingredient is selected from the group consisting of an acid, ahydrotrope, a thickener, a binder, a dispersant polymer, a carriermedium, a surfactant, a perfume, a dye, and mixtures thereof.
 19. Aprocess for preparing an in-situ water-soluble zinc salt for use as abase or additive in preparing an automatic dishwashing composition, saidprocess comprising the steps of: a) dispersing zinc oxide in water; b)combining an acid with said zinc oxide/water mixture; wherein said acidis selected from the group consisting of acetic acid, aspartic acid,benzoic acid, boric acid, bromic acid, formic acid, glutamic acid,hydrochloric acid, lactic acid, malic acid, nitric acid, sulfamic acid,sulfuric acid, tartaric acid, and mixtures thereof; c) mixing said zincoxide/water mixture and said acid until said zinc oxide is at leastpartially dissolved; and d) combining said zinc oxide/water/acid mixturewith at least one detergent ingredient to form a detergent composition.20. A process according to claim 19, wherein said acid is provided atleast in an amount determined stoichimetrically using the formula:2H_(x)A+XZnO→XZnA_(2/x)+XH₂O wherein A is an organic and/or an inorganicacid, and x is an integer that varies from 1 to
 2. 21. A processaccording to claim 19 wherein said at least one detergent ingredient isselected from the group consisting of a detergent builder, alkalinitybuilder, bleach, enzyme, surfactant, defoamer, polymer and mixturesthereof.